The present invention relates to an electrolytic cell, in particular for the electrolytic production of chlorine and alkali, hypochlorites and chlorates, and to a method for manufacturing an electrolytic cell according to the invention, especially a method for attaching the conductor rails to the shell part of the electrolytic tank, especially to a shell part having an anode potential, and to a method for the electrolytic production of metals, especially a method for attaching suspended conductors to titanium electrodes.
Titanium anodes coated with noble metals or their oxides are very often used nowadays for the production of chlorine and alkali, hypochlorites and chlorates. These anodes are very often connected to the conductor rail by using, for example, a gasketed screw joint passing through the wall of the electrolytic tank. Joints of this type or similar joints, e.g. flange joints, can also be used for the attachment of parts made of metals other than titanium to the conductor rail. One example is the titanium tube/copper core electrode arm, in which the copper core has been attached, by a threading in it, to the anode itself, and at its other end by means of a screw joint to the wall of the electrolytic tank and to the conductor rail. All screw joints have the disadvantage that they cause transition resistance in the contact surfaces and thereby losses of energy. Screw joints inside the electrolytic tank are also disadvantageous in the respect that the electrolytic solution can enter the joint and cause corrosion, especially if different materials have been attached to each other, and in practice the gaskets used in screw joints lead to a great number of maintenance operations. Furthermore, titanium screw joints result in a long and poorly conductive titanium current path.
Aluminum conductor rails have been connected to the end of titanium electrodes even directly, without screw joints. An aluminum lump can be cast into the arm of an electrode passing through the shell part of the cell, and this aluminum lump for its part is attached by, for example, a screw joint to an aluminum conductor rail, as disclosed in British Pat. No. 1,127,484. Thereby the titanium current path becomes relatively long, and causes losses of energy owing to the poor electrical conductivity of titanium. In addition, the long arm of the electrode causes additional consumption of titanium. Casting the ends of the ribs in aluminum is a cumbersome work stage.
The joint between the conductor rail and a titanium anode has also been made by attaching the electrode by bolts to anode supports situated inside the electrolytic tank. These supports can be resistance welded in one stage to the titanium shell part, and this, for its part, can be resistance welded to an aluminum conductor, provided that the thickness of the aluminum is less than 3 mm, as explained in British Pat. No. 1,125,493. This construction has a weakness mainly in that it is not applicable to cases where the conductor rail is thick, as is the case when large flows and high flow densities are used. When thin aluminum plates are involved, the aluminum surface layer must be attached to the aluminum current conductor by a separate joint. The same is true for the other methods of coating titanium with aluminum mentioned in this patent, e.g. explosive welding. In this case the making of inlets, e.g. pipe block, becomes complicated, and furthermore, such a construction is expensive.
German Application DOS 2603626 discloses another solution for attaching an aluminum conductor rail to the shell part of a titanium electrolytic tank. In this case a copper, aluminum, steel or titanium tenon has been attached to the titanium shell part by means of friction or condenser-discharge bolt welding. The aluminum tenon can then be embedded into bores in the conductor rail and welded to the rail. This construction has a disadvantage in that, owing to the poor electrical conductivity of titanium, a large number of the said aluminum tenons are required for conducting current into the electrolytic tank.
As mentioned previously, the titanium anodes can be attached with bolts to supports welded to the inner surface of the titanium shell part, whereby transition resistance is produced in the contact surfaces. On the other hand, German Application DOS 2603626 discloses the cleat welding of an anode plate, bent at its upper edge, to the support strips. It also discloses that the anodes can be welded directly to the upper surface of the metallic base plate. The above attaching method is disadvantageous in the respect that during the welding the anode plates must somehow be directed so that they will attach to the right point.
The object of the present invention is therefore to provide an electrolytic cell in which the current path between, on the one hand, the conductor rails or suspended conductors connected to one pole of the source of current and, on the other hand, their electrodes is as short as possible and the transition resistance is as low as possible.